Concepts for Standardized Shape Memory Actuators for Positioning Applications

Actuators based on shape memory alloys (SMAs) have been developed to be used only in special applications. Therefore solutions based on SMAs generally cannot be transferred to other tasks. Focusing on the development for special applications has two important disadvantages. Firstly, the effort and costs reach a high level due to the individual development and secondly, for many companies the development of complex SMA-actuators turns out to be an insuperable barrier. Reasons for this are the complex characteristics and the missing simulation and design tools. In order to make statements about the functions and durability of the SMA-component, extensive tests need to be conducted. As a result there is a significant interest in providing SMA-actuator systems with complex and also variable functions. Modular systems allow a transfer to different areas of applications and they also lead to a reduction of variants. Using standardized components is an interesting opportunity to reduce the risk of individual development and the effort for single applications effectively. However, the increased system complexity of conventional modular systems is a problem (additional functions are required, e.g. the mechanical and electrical coupling of the modules). Apart from the conventional form of a modular system there is the possibility of a variable SMA-actuator system generated by standardized SMA-components which can be assembled to a stack system. The existing and unique potential of SMAs for function integration and therefore standardization can be used to its full extent. The aim of this paper is to show an application of such an SMA-actuator in stack design. Besides, the study presents the development process and the control concept of this actuator. An actuator system like this can be used in positioning solutions, for example. The task of this variable SMA-actuator is the conversion of a controller output variable into an exact displacement. The evidence of the realization of simple SMA-based actuators in modular design is provided with the development of this actuator system.